The invention relates to a load receiver and a loading stage, and it also relates to a balance, particularly a mass comparator, that is equipped with the inventive load receiver and/or loading stage. The load receiver has an arrangement of narrow ridges and a horizontal receiving surface for a weight, with a depression or concavity so that the center of the load receiver is lower than the peripheral portions. The loading stage supports at least one weight-loading device, which can be connected to the loading stage and is shaped so that the load receiver reaches from below through the weight-loading device without touching the latter. The loading stage and the load receiver are movable up and down in relation to each other.
A load receiver with a funnel-shaped depression at the center as disclosed in U.S. Pat. No. 5,332,870 is designed for the specific purpose of weighing flat filters. The conical surface of the load receiver consists of a net or a metal foil with perforations.
Loading stages are found in comparator balances for masses and volumes and serve to automatically interchange weights that are being compared to each other. This type of balance is used for the exact determination of masses and volumes of weight standards, primarily in governmental institutes of metrology. The comparison weighings often involve weights of different sizes.
A mass comparator balance with a load receiver designed for weights of unequal size is described in the German utility model DE U 295 17 368. It has a freely suspended load receiver with an arrangement of narrow ridges to support the weight standards that are to be tested. A weight-exchanging mechanism has a weight-loading and -unloading plate perforated by slots. When the weight-exchanging mechanism lowers the loading/unloading plate to set a weight on the load receiver, the ridges of the load receiver pass through the slots and take up the weight. The arrangement of narrow ridges of the load receiver consists of at least four branches that are joined by a connecting ridge. This design also allows a plurality of weights of different sizes to be weighed together with the highest degree of accuracy.
It is possible that a weight comparison involves test masses of different shapes, such as spherical weights, cylindrical weights with knobs, or disc-shaped weights. This makes it necessary to place individual weights of different shape and size in an exactly centered position on the load receiver, e.g., to limit the magnitude of eccentric loading errors as much as possible and, as an ultimate purpose, to perform a precise comparison that is independent of the shapes of the masses being compared. The mass comparator according to the last-mentioned reference does not meet this requirement, based on the design of its load receiver and/or weight-changing mechanism.